In a variety of semiconductor device fabrication processes, a semiconductor wafer is heated or cooled and the desired fabrication process occurs on the temperature controlled semiconductor substrate. To establish good manufacturing process control, the semiconductor substrate should have a uniform temperature distribution across its entire surface to avoid fabrication process nonuniformities and manufacturing yield loss.
Conventional semiconductor processing reactors, however, are unable to effectively provide a uniform temperature distribution across the entire semiconductor wafer surface, especially at higher processing temperatures. Further, conventional fabrication reactors do not have the flexibility to operate over a wide range from low temperature processing to high temperature processing while still maintaining a uniform temperature distribution across the semiconductor wafer. Higher processing temperatures (e.g., 300.degree. C. to 1000.degree. C.) are required for a variety of device fabrication process steps in silicon technologies. These include chemical-vapor deposition (CVD) processes and plasma-enhanced CVD (PECVD) processes for deposition of various material layers. Other thermally activated high temperature device fabrication processes include thermal anneals for implant activation and dopant redistribution as well as thermal oxidations. On the other hand most plasma etch processes usually require lower substrate temperatures (e.g., -150.degree. C. to 150.degree. C.).